Since the late 1990s when the first civil aircraft had Federal Aviation Administration (FAA) supplemental type certificates (STCs) for night vision goggles (NVG) flight, modification companies in the aviation field have been trying to improve the crew station space of the pilots, tactical flight officers (TFOs) and observers who are using the NVG during fight. The original lighting adapted from the military was green, which worked well for the infrared (IR) suppression in the crew station lights but had drawbacks from issues caused due to the green light shifting the colors on the instrument dials along with the various maps and charts used during flight: yellow appeared green; red appeared brown and so on. Concerns arose when caution/warning annunciators came into play and how the pilot would react to the shift of yellow and red colored annunciator caps.

White filters

In the early 2000s, white phosphor night vision imaging systems (NVISs) arrived, and a night vision filter that maintains the true color of the instrument range markings, annunciators, displays, charts and maps. The NVIS white filter has a higher IR signature but not enough to interfere with the NVG wearer’s visual acuity. The NVG operator’s most important criteria while using the goggles is visual acuity through the NVG, both looking outside the aircraft and while scanning the flight and engine instruments. White NVIS has been the standard since then.

The NVG operator’s most important criteria while using the goggles is visual acuity

The filters are being used internally on the instruments, the panels and displays, or as a cover glass or lighted bezel around electromechanical instruments. They are also used predominately in post lights, flood lights, and utility lights. The onset of flat panel displays being used in lieu of desired indicators presented a troublesome issue for the NVG modification shops. Many of the filters that they were using were not produced with large enough dimensions needed to cover the display screen. Now most of the flat panel multi-function displays are filtered internally at the light source either by the manufacturer or the modification shop. There are still many displays that are best filtered externally with a topical filter used between the display and pilot’s eye. These filters range anywhere between 55 to 75 per cent transmission, meaning that, although they are blocking the IR from the display screen and any related buttons, they are also cutting the luminance transmissions by 25 to 45 per cent from the designed brightness by the original equipment manufacturer.

Difficulty during daytime

Current filters are being used that block IR but will also increase the contrast of the displays. These current filters work well at night where the displays are very low in IR and sufficient in luminance output. During daylight flights, the filtering became more difficult to read especially on displays that barely produced sunlight readability prior to being filtered; a filter applied to the display in this situation cuts the brightness of the display by up to 45 per cent. Where this is most problematic is on sunny days where the sun is shining directly onto the display in flight, decreasing the contrast of the display, and when the pilot is flying into the sun and his pupils contract due to the brightness so there is not enough luminance from the display to be able to discern the data on the screen.

Modification companies have worked with filter manufacturers to ensure that filter transmission is the top priority

Technically, there have been only minor advancements to NVG filters over the past 10 to 12 years. Modification companies have worked with filter manufacturers to ensure that filter transmission is the top priority. The tubes now being produced and used in the newer NVG have advanced to the point where the IR of a filtered display or annunciator is seldom ever a serious problem due to the auto-gated technology of the tubes.

Although there have not been many changes involving NVG lighting inside the aircraft, exterior lights such as searchlights, and landing and taxi lights are making large advancements in NVG flying capabilities.

External lighting – the next evolution

Whether it’s air medical, law enforcement or military, all operators have similar issues, balancing new equipment with available amperage, weight and flight crew workload. At REBTECH, we have focused on auxiliary solutions that enhance NVIS operations while increasing safety during critical phases of flight over the past 13 years. It’s imperative for the aircrew to identify the landing area quickly, and clearly observe any obstructions prior to making a landing in an unimproved area. And while the aircraft is on the ground, it should be properly illuminated to ensure the safety of the personnel to prevent tail or even main rotor strikes.

Currently aircraft are equipped with taxi and landing lights, a third-party retractable searchlight, third-party cameras, third-party scene lights and perhaps a hover and/or logo lights, all requiring weight and power requirement issues. Having a multitude of equipment from a variety of OEMs means more spares, more maintenance, and more aircraft on ground (AOG) issues, but it is unavoidable as they are all necessary safety equipment for the air crew as well as ground personnel.

Solution to a problem

Having a completely integrated system with a low weight, as well as making a weight saving from removal of existing equipment, would allow for additional power for medical equipment to support patients, for communications devices and for any other required devices, as well as extend the aircrew’s capabilities. Adding tablet app functionality would provide an analog aircraft with video capabilities, without a major avionics upgrade.

Operating at night has come a long way since the late 1990s, and it still has some way to go to make low or no-light operations even safer, easier and more efficient

With this in mind, my team at REBTECH has set out to design and produce a >25 million candela steerable searchlight (long, medium and wide), with landing, taxi, elliptical, scene right, scene left, hover, and hoist lighting all included into one fixture, weighing just 25lbs and operating at 25A. We also included an IR / short wavelength IR camera system and/or a 360° aircraft view. Plus, we designed it to have a choice of controllers from handheld to panel mounted or via an Apple/iPad app as well as supporting existing cyclic controls. Technology and engineering have caught up to a point at which several new products have or will hit the market over the next six months.

Operating at night has come a long way since the late 1990s, and it still has some way to go to make low or no-light operations even safer, easier and more efficient. I hope I am contributing in some regard to help progress this technology in aiding aviators and operators.